- Email: [email protected]
Comparison of conventional and microwave sintered ferrous alloys
It was noted that evaluation of flow properties of powders, less than 325 mesh, presents difficulties in ranking, although these have high flowability. It was suggested that a torque rheometer can detect differences in dry viscosify of non-agglomerated powders. A study of this to detect friction related differences between samples of gas atomized stainless steel powder, was described. Both fine samples, less than 325 mesh, and mixtures with larger particles were examined. Results from the torque rheometer and standard tests for flowability were compared. It was shown that the torque rheometer is of value in evaluat,ing flowabiliity of very fine powders. ON-LINE DROPLET FOR PRODUCTION SOLDER POWDERS
SIZE CONTROL OF SPHERICAL
J.C.Rocha, eJ.H.Chun. (Massachusetts Inst. of Technology, USA.) Production of uniform spherical solder particles, by a Uniform Droplet Spray technique was outlined. The need for precision in particle size for electronics applications was noted. Closed loop control of the process to make particles in the 75 to 1000 pm size range was discussed. Two parts of the system were identified, droplet size measurement and sphere size control. It was shown that the particle size can be controlled within +2.5% of the target size. The emphasis of the study was on particle sizes 250 to 800 pm.
Sin tering SINTERING OF MOLYBDENUM CIDE DOPED WITH NICKEL
DISILI-
I.H.Moon et al. (Hanyang University, Seoul, Korea.) Sintcring of ball milled MoSi,-(0.1 to 2)wt%Ni was investigated during hcating at 4, 8 and lG”C.min-’ and isothermally. The process was followed by X-ray diffraction and microscopy. GNi,Si was detected. The powder sintered readily at 1250 to 1300°C. Grain growth in the 2%Ni alloy was examined as a function of time during liquid phase sintering at 1400°C. SINTERING AND CRYSTALLIZATION OF STRONTIUM OXIDE-ALUMINA-SILICA CERAMICS Y.M.Sung et al. (I)aejon University, Korea.) A study of sintering of 50wt%(SrOSiOz)-5O%(SrO-A&O,-SiO,), prepared by melting and milling in an aZr0, mill was described. The glass transition and crystallization temperatures were determined and activation energy calculated. Powders were compacted and sintered
at 900°C and then at 1100°C. Densities and structures at’the sintered ceramics were measured. Effects of BaO, and TiO, additions were studied. The results were compared with data for stoichiometric SrO-A&O,-SiO, materials. MECHANICAL PROPERTIES AND SINTERING OF WATER ATOMIZED IRONCHROMIUM-MOLYBDENUM POWDERS C.Lindberg. (IIoganas AB, Hoganas, Sweden. 1 PM Cr-Mo st,eels were discussed with reference to mechanical properties, sintering characteristics, hardenability and the tendency for Cr to oxidize. It was shown that by preparing pre-alloyed 3%Cr-0.58Mo steel, pressing and sintering at 1120°C in N-H oxidation could be minimized. Yield strengths of 500 to 570 MPa and Vickers hardness of 220 to 260 could be attained at 0.3 to 0.4%C.
fliA1, with Cr, Mn and Mg alloy additions, was processed by mechanical alloying and sintered by a pulse discharge technique. Sintering was rapid. The best improvement in mechanical properties was obtained with 2%Cr. It was shown that the fracture strength increased with increased test temperature with Cr added. Mn had the reverse effect. MICROWAVE SINTERING AND CHARACTERIZATION OF POWDERED METALS R.Roy et al. (Pennsylvania University, USA. 1 1Jse of microwave sintering
was discussed and it was noted that few experiments have been done with metal powders. Green laboratory and commercial compacts were microwave sintered, typically, at 1100 to 1300°C for 5 to 30 min-
GRAVITY INDUCED DIMENSIONAL NON-UNIFORMITY TAKING GRAIN SEGREGATION INTO ACCOUNT
utes. ed to with with
E.A.Olevsky, sylvania State
Dimensional
R.M.German. USA.) University,
(Penn-
Liquid phase sintering, under simultaneous influence of surface tension and gravity, was analysed and mathematically modelled using continuum theory taking grain segregation into account. The model was applied to sintering of a porous cylindrical specimen. Shape distortion was characterized and compared wit,h experimental data for W-Fe-Ni samples. The effect of gravity segregation on dimensional non-uniformity was determined. The application of the study was shown to lie in the need for improved dimensional precision in sintered parts and to develop a model to give better tool design to achieve this. DIRECT OBSERVATION OF PM PARTS DURING SINTERING R.M.German ef al. (Pennsylvania State University, USA.) It was reported that in situ video imaging had been used to study densification and distortion during sintering of a range of alloys. Various phenomena were directly observed. The technique was said to provide a tool for process optimization. Results were correlated with data obtained by other methods.
State
The sintered compacts were reporthave unifurmly distributed porosity properties improved in comparison conventionally process materials.
control
COMPARISON OF CONVENTIONAL AND MICROWAVE SINTERED FERROUS ALLOYS M.J.Yang, R.M.German. (Pennsylvania State University, USA.) FC0208, Fe-Cu-C, and FN0208, Fe-
Ni-C steels were conventionally and microwave sintered at a range of temperatures after pressing at 552 and 690 MPa. The sintered samples were characterizcd for properties, dimensions, SC! and structure. Microwave sintering was reported to result in higher strength and hardness but worse dimensional control and non-uniform microstructure. The need for further investigation of microwave sintering was emphasized. PREDICTION OF DIMENSIONAL CHANGE DURING SINTERING OF STEEL R.M.German et al. (Pennsylvania State University, USA. 1 It was reported that a model had been applied to the prediction of dimensional change during sintering of FC0208, Fe-Cu-C steel. The model incor-
Novel sintering techniques
porates mechanisms involved in sintering and was validated by dilatometry. The predictions were shown to be in agreement with data from industrial processing.
EFFECT OF ALLOYING ON flITANIUM ALUMINIDE PREPARED BY PULSE DISCHARGE SINTERING
EFFECT OF SEVERAL PARAMETERS ON PART DISTORTION DURING SINTERING
T.Abe et al. (Tohoku National Industrial Research Inst., Sendai, Japan.)
A.Vovan, Canada.)
M.Guillot.
(Lava1
University,
MPR June 2000
37
Use of finite element modelling to predict final part dimensions, from green density distributions, was reported. Green density data may not be enough to predict final dimensions. It has been shown that temperature differences may exist in a part. Final dimensions may also be influenced by gravity, friction, gas distribution in the sintering furnace and part orientation. The effects of these on dimensional changes in a stainless steel part were presented. Friction, as well as thermal inertia in the sintering trays, is shown to play a significant role in part distortion.
Hard metal processing INTERACTION OF CHROMIUM WITH COBALT IN DIAMOND TOOL MATRIXES (E.P.F.L., D.A.Akytiz, H.Hofmann. Switzerland.) Addition of Cr to Co matrix, in diamond tools, to enhance the bond between diamond particle and matrix, was noted. There was shown to be interaction between Cr and C and Cr and Co Cr was shown to influence the proportions of hexagonal and cubic Co due to the effect of Cr on the transition temperature, replacement of Co oxides by Cr oxides and porosity induced by the Kirkendal effect. Matrix Vickers hardness decreased with increase in %Cr but remained above 310. INFLUENCE OF COBALT CHARACTERISTICS ON BARDMETAL PROCESSING CONDITIONS M.Oehlers et al. (Union Mini&r-e, Belgium.) A newly available ultrafine Co powwith standard der was compared extrafine Co powder in WC-Co hardmetals. The WC grain size was 2 to 3 pm, and 10 and 2O%Co materials were prepared. The novel powder was shown to allow reduction of the milling time. Sintering data were presented and discussed. In terms of environmental considerations the new powder did not require different process conditions when used as granulated powder with up to 2% organic binder. ATYPICAL MICROSTRUCTURE TUNGSTEN CARBIDE-COBALT
IN
F.J.Arenas et al. (Caracas Technical University, Caracas, Venezuela.) Uniaxially pressed WC-12%Co-VC compacts were vacuum sintered at 1300 and 1350°C for 30 minutes. Microstructures were analysed quantitatively; contiguity, particularly, was measured. An atypical microstructure was found, which increased with increase in %VC. In samples with this atypical structure 38
MPR June 2000
higher Vickers hardness values, of 1750 and 1830, were found. MICROSTRUCTURAL INVESTIGATIONS OF GRADED BARDMETALS J.L.Garcia et al. (Technical University of Vienna, Vienna, Austria.) Functionally graded hardmetals were discussed. These have a smooth variation in phase proportions, with or without layers, in the near surface microstructure. Layers may form jagged interfaces which interlock the phase bands and allow thermal and mechanical loads to be transmitted smoothly. investigations of Microstructural (Ti,W)C based materials were described. A stress analysis of the outermost layer was carried out using a Seemann-Bohlin X-ray diffraction technique.
Particle size and injection rates were varied. Structure and properties of the materials were investigated to ensure production of a homogeneous material.
Properties materials
of PM
HEAT TREATMENT OF SINTERED AND COLD FORGED ALUMINIUM-TINCOPPER-MAGNESIUM ALLOY PARTS
Spray forming
(Alspors al. A.I.Lintvintsev it Technology Ltd, Russia.) Al-Sn-Cu-Mg alloy parts were pressed from powder, liquid phase sintered and cold forged. Effects of sintering time and temperature on properties were determined. Precipitation phenomena were detected. The investigations were shown to allow optimization of heat treatment to final Brine1 hardness of 65 to 100 or 105.
LOW CARBON STEEL AS SPRAY FORMING MODEL MATERIAL
METAL INJECTION MOULDING OF TUNGSTEN HEAVY ALLOY
P.Mayr et al. (Stiftung Inst. fur Werkstofftechnik, Germany.) Spray forming for shaping materials was discussed with reference to the need for further research. A study of the structures of spray formed low carbon steel, to determine principles of solidification, was described. Pores were the most common defects. The incidence of pores was reduced by spray forming in Ar. Use of N required addition of Al to the melt to reduce porosity but this altered the structure. Thermal and thermo-mechanical treatment of spray formed billets gave a fine microstructure with improved properties.
I.H.Moon et al. (Hanyang University, Korea.) W heavy alloys were fabricated by injection moulding with a binder based on methylcellulose-water with additions of Ni and Fe chloride. Moulding characteristics were studied as a function of the binder properties. Moulding was at 130°C debinding at 700°C and sintering at 1480°C. Near full density was attained. It was suggested that, due to sintered the the uniformity of microstructure, the additions of Ni and Fe chloride are beneficial.
PROCESSING AND PROPERTIES OF SPRAY FORMED HSS ROLLING MILL ROLL SLEEVES R.M.F.Jones,R.L.Kennedy. (Allvac,USA.) Use of roll sleeves made from high speed steel to improve mill performance in respect of product dimensional accuracy was noted. The paper described use of spray forming to produce roll sleeves, at reduced cost. The spray formed material was shown to have the fine structure found in conventional PM materials. The high speed steel sleeve preforms were converted into sleeve blanks by ring rolling or upset press forging. MANUFACTURE OF PARTICLE REINFORCED STEELS BY SPRAY FORMING J.Banhart et al. (Fraunhofer Inst., Germany. ) It was reported that ceramic particle reinforced steel had been made by injecting the particles into the atomization spray zone. SIC, WC and Al,O, were used.
EROSION-CORROSION OF TITANIUM CARBIDE-NICKEL-MOLYBDENUM CERMETS J.Pirso et al. (Tallinn Technical University, Estonia.) Erosion-corrosion of Tic-(Ni,Mo) cermets in acid sluries of SiO, was investigated. The performance of the cermets was shown to depend on the composition and proportion of the binder in the cermet. The performance improved as the %TiC and %Mo were increased. Effects of other hard particles were studied. Performance was improved by addition of Cr,C,. Material removal mechanisms in testing were examined by electron microscopy of eroded surfaces. Processes included binder removal, cracking and particle pull-out.
Hot isostatic pressing MICROSTRUCTURE AND PROPERTIES OF HIP PM SUPERALLOY 718 U.Habel. (Crucible USA.)
Compaction
Metals,
SIZE CONTROL OF SPHERICAL
J.C.Rocha, eJ.H.Chun. (Massachusetts Inst. of Technology, USA.) Production of uniform spherical solder particles, by a Uniform Droplet Spray technique was outlined. The need for precision in particle size for electronics applications was noted. Closed loop control of the process to make particles in the 75 to 1000 pm size range was discussed. Two parts of the system were identified, droplet size measurement and sphere size control. It was shown that the particle size can be controlled within +2.5% of the target size. The emphasis of the study was on particle sizes 250 to 800 pm.
Sin tering SINTERING OF MOLYBDENUM CIDE DOPED WITH NICKEL
DISILI-
I.H.Moon et al. (Hanyang University, Seoul, Korea.) Sintcring of ball milled MoSi,-(0.1 to 2)wt%Ni was investigated during hcating at 4, 8 and lG”C.min-’ and isothermally. The process was followed by X-ray diffraction and microscopy. GNi,Si was detected. The powder sintered readily at 1250 to 1300°C. Grain growth in the 2%Ni alloy was examined as a function of time during liquid phase sintering at 1400°C. SINTERING AND CRYSTALLIZATION OF STRONTIUM OXIDE-ALUMINA-SILICA CERAMICS Y.M.Sung et al. (I)aejon University, Korea.) A study of sintering of 50wt%(SrOSiOz)-5O%(SrO-A&O,-SiO,), prepared by melting and milling in an aZr0, mill was described. The glass transition and crystallization temperatures were determined and activation energy calculated. Powders were compacted and sintered
at 900°C and then at 1100°C. Densities and structures at’the sintered ceramics were measured. Effects of BaO, and TiO, additions were studied. The results were compared with data for stoichiometric SrO-A&O,-SiO, materials. MECHANICAL PROPERTIES AND SINTERING OF WATER ATOMIZED IRONCHROMIUM-MOLYBDENUM POWDERS C.Lindberg. (IIoganas AB, Hoganas, Sweden. 1 PM Cr-Mo st,eels were discussed with reference to mechanical properties, sintering characteristics, hardenability and the tendency for Cr to oxidize. It was shown that by preparing pre-alloyed 3%Cr-0.58Mo steel, pressing and sintering at 1120°C in N-H oxidation could be minimized. Yield strengths of 500 to 570 MPa and Vickers hardness of 220 to 260 could be attained at 0.3 to 0.4%C.
fliA1, with Cr, Mn and Mg alloy additions, was processed by mechanical alloying and sintered by a pulse discharge technique. Sintering was rapid. The best improvement in mechanical properties was obtained with 2%Cr. It was shown that the fracture strength increased with increased test temperature with Cr added. Mn had the reverse effect. MICROWAVE SINTERING AND CHARACTERIZATION OF POWDERED METALS R.Roy et al. (Pennsylvania University, USA. 1 1Jse of microwave sintering
was discussed and it was noted that few experiments have been done with metal powders. Green laboratory and commercial compacts were microwave sintered, typically, at 1100 to 1300°C for 5 to 30 min-
GRAVITY INDUCED DIMENSIONAL NON-UNIFORMITY TAKING GRAIN SEGREGATION INTO ACCOUNT
utes. ed to with with
E.A.Olevsky, sylvania State
Dimensional
R.M.German. USA.) University,
(Penn-
Liquid phase sintering, under simultaneous influence of surface tension and gravity, was analysed and mathematically modelled using continuum theory taking grain segregation into account. The model was applied to sintering of a porous cylindrical specimen. Shape distortion was characterized and compared wit,h experimental data for W-Fe-Ni samples. The effect of gravity segregation on dimensional non-uniformity was determined. The application of the study was shown to lie in the need for improved dimensional precision in sintered parts and to develop a model to give better tool design to achieve this. DIRECT OBSERVATION OF PM PARTS DURING SINTERING R.M.German ef al. (Pennsylvania State University, USA.) It was reported that in situ video imaging had been used to study densification and distortion during sintering of a range of alloys. Various phenomena were directly observed. The technique was said to provide a tool for process optimization. Results were correlated with data obtained by other methods.
State
The sintered compacts were reporthave unifurmly distributed porosity properties improved in comparison conventionally process materials.
control
COMPARISON OF CONVENTIONAL AND MICROWAVE SINTERED FERROUS ALLOYS M.J.Yang, R.M.German. (Pennsylvania State University, USA.) FC0208, Fe-Cu-C, and FN0208, Fe-
Ni-C steels were conventionally and microwave sintered at a range of temperatures after pressing at 552 and 690 MPa. The sintered samples were characterizcd for properties, dimensions, SC! and structure. Microwave sintering was reported to result in higher strength and hardness but worse dimensional control and non-uniform microstructure. The need for further investigation of microwave sintering was emphasized. PREDICTION OF DIMENSIONAL CHANGE DURING SINTERING OF STEEL R.M.German et al. (Pennsylvania State University, USA. 1 It was reported that a model had been applied to the prediction of dimensional change during sintering of FC0208, Fe-Cu-C steel. The model incor-
Novel sintering techniques
porates mechanisms involved in sintering and was validated by dilatometry. The predictions were shown to be in agreement with data from industrial processing.
EFFECT OF ALLOYING ON flITANIUM ALUMINIDE PREPARED BY PULSE DISCHARGE SINTERING
EFFECT OF SEVERAL PARAMETERS ON PART DISTORTION DURING SINTERING
T.Abe et al. (Tohoku National Industrial Research Inst., Sendai, Japan.)
A.Vovan, Canada.)
M.Guillot.
(Lava1
University,
MPR June 2000
37
Use of finite element modelling to predict final part dimensions, from green density distributions, was reported. Green density data may not be enough to predict final dimensions. It has been shown that temperature differences may exist in a part. Final dimensions may also be influenced by gravity, friction, gas distribution in the sintering furnace and part orientation. The effects of these on dimensional changes in a stainless steel part were presented. Friction, as well as thermal inertia in the sintering trays, is shown to play a significant role in part distortion.
Hard metal processing INTERACTION OF CHROMIUM WITH COBALT IN DIAMOND TOOL MATRIXES (E.P.F.L., D.A.Akytiz, H.Hofmann. Switzerland.) Addition of Cr to Co matrix, in diamond tools, to enhance the bond between diamond particle and matrix, was noted. There was shown to be interaction between Cr and C and Cr and Co Cr was shown to influence the proportions of hexagonal and cubic Co due to the effect of Cr on the transition temperature, replacement of Co oxides by Cr oxides and porosity induced by the Kirkendal effect. Matrix Vickers hardness decreased with increase in %Cr but remained above 310. INFLUENCE OF COBALT CHARACTERISTICS ON BARDMETAL PROCESSING CONDITIONS M.Oehlers et al. (Union Mini&r-e, Belgium.) A newly available ultrafine Co powwith standard der was compared extrafine Co powder in WC-Co hardmetals. The WC grain size was 2 to 3 pm, and 10 and 2O%Co materials were prepared. The novel powder was shown to allow reduction of the milling time. Sintering data were presented and discussed. In terms of environmental considerations the new powder did not require different process conditions when used as granulated powder with up to 2% organic binder. ATYPICAL MICROSTRUCTURE TUNGSTEN CARBIDE-COBALT
IN
F.J.Arenas et al. (Caracas Technical University, Caracas, Venezuela.) Uniaxially pressed WC-12%Co-VC compacts were vacuum sintered at 1300 and 1350°C for 30 minutes. Microstructures were analysed quantitatively; contiguity, particularly, was measured. An atypical microstructure was found, which increased with increase in %VC. In samples with this atypical structure 38
MPR June 2000
higher Vickers hardness values, of 1750 and 1830, were found. MICROSTRUCTURAL INVESTIGATIONS OF GRADED BARDMETALS J.L.Garcia et al. (Technical University of Vienna, Vienna, Austria.) Functionally graded hardmetals were discussed. These have a smooth variation in phase proportions, with or without layers, in the near surface microstructure. Layers may form jagged interfaces which interlock the phase bands and allow thermal and mechanical loads to be transmitted smoothly. investigations of Microstructural (Ti,W)C based materials were described. A stress analysis of the outermost layer was carried out using a Seemann-Bohlin X-ray diffraction technique.
Particle size and injection rates were varied. Structure and properties of the materials were investigated to ensure production of a homogeneous material.
Properties materials
of PM
HEAT TREATMENT OF SINTERED AND COLD FORGED ALUMINIUM-TINCOPPER-MAGNESIUM ALLOY PARTS
Spray forming
(Alspors al. A.I.Lintvintsev it Technology Ltd, Russia.) Al-Sn-Cu-Mg alloy parts were pressed from powder, liquid phase sintered and cold forged. Effects of sintering time and temperature on properties were determined. Precipitation phenomena were detected. The investigations were shown to allow optimization of heat treatment to final Brine1 hardness of 65 to 100 or 105.
LOW CARBON STEEL AS SPRAY FORMING MODEL MATERIAL
METAL INJECTION MOULDING OF TUNGSTEN HEAVY ALLOY
P.Mayr et al. (Stiftung Inst. fur Werkstofftechnik, Germany.) Spray forming for shaping materials was discussed with reference to the need for further research. A study of the structures of spray formed low carbon steel, to determine principles of solidification, was described. Pores were the most common defects. The incidence of pores was reduced by spray forming in Ar. Use of N required addition of Al to the melt to reduce porosity but this altered the structure. Thermal and thermo-mechanical treatment of spray formed billets gave a fine microstructure with improved properties.
I.H.Moon et al. (Hanyang University, Korea.) W heavy alloys were fabricated by injection moulding with a binder based on methylcellulose-water with additions of Ni and Fe chloride. Moulding characteristics were studied as a function of the binder properties. Moulding was at 130°C debinding at 700°C and sintering at 1480°C. Near full density was attained. It was suggested that, due to sintered the the uniformity of microstructure, the additions of Ni and Fe chloride are beneficial.
PROCESSING AND PROPERTIES OF SPRAY FORMED HSS ROLLING MILL ROLL SLEEVES R.M.F.Jones,R.L.Kennedy. (Allvac,USA.) Use of roll sleeves made from high speed steel to improve mill performance in respect of product dimensional accuracy was noted. The paper described use of spray forming to produce roll sleeves, at reduced cost. The spray formed material was shown to have the fine structure found in conventional PM materials. The high speed steel sleeve preforms were converted into sleeve blanks by ring rolling or upset press forging. MANUFACTURE OF PARTICLE REINFORCED STEELS BY SPRAY FORMING J.Banhart et al. (Fraunhofer Inst., Germany. ) It was reported that ceramic particle reinforced steel had been made by injecting the particles into the atomization spray zone. SIC, WC and Al,O, were used.
EROSION-CORROSION OF TITANIUM CARBIDE-NICKEL-MOLYBDENUM CERMETS J.Pirso et al. (Tallinn Technical University, Estonia.) Erosion-corrosion of Tic-(Ni,Mo) cermets in acid sluries of SiO, was investigated. The performance of the cermets was shown to depend on the composition and proportion of the binder in the cermet. The performance improved as the %TiC and %Mo were increased. Effects of other hard particles were studied. Performance was improved by addition of Cr,C,. Material removal mechanisms in testing were examined by electron microscopy of eroded surfaces. Processes included binder removal, cracking and particle pull-out.
Hot isostatic pressing MICROSTRUCTURE AND PROPERTIES OF HIP PM SUPERALLOY 718 U.Habel. (Crucible USA.)
Compaction
Metals,